Design of an electron cooling device for the accumulator cooler ring in MUSES project

As a part of new experimental facility in the Radio Isotope Beam Factory (RIBF) project at RIKEN, the Multi-Use Experimental Storage rings (MUSES) have an Accumulator Cooler Ring (ACR) which is used for both the accumulation and cooling of RI beams and various experiments. Besides a stochastic cooler, an electron cooler (EC) is presently under development. The ion energy in the ACR ranges from 60 to 400 MeV/u which corresponds to the electron beam (e-beam) energy for the EC from 30 to 250 kV. The maximum current from a 12.7 mm cathode is 4.1 A with a gun perveance of 0.79 μP. A superconducting solenoid in the gun section generates a magnetic field of 4 T which corresponds to a factor of 20 in adiabatic expansion. The design issues of the gun section, collector, toroidal magnets and compensation solenoids are discussed in detail with some retrospection of the development.